1. Field
The present disclosure relates to a light emitting device that uses excitation light, and specifically, to a light emitting device that uses, as illumination light, light including fluorescence which is generated by radiating excitation light to a light emitting section including a phosphor and an illumination device that includes the light emitting device.
2. Description of the Related Art
A light emitting device which includes a semiconductor laser or the like as an excitation light source and performs illumination or the like using excitation light emitted from the excitation light source has been proposed lately. A light emitting device that uses such excitation light is proposed in, for example, Japanese Unexamined Patent Application Publication No. 2005-150041 (published on Jun. 9, 2005), Japanese Unexamined Patent Application Publication No. 2004-111909 (published on Apr. 8, 2004), Japanese Unexamined Patent Application Publication No. 2012-099222 (published on May 24, 2012), and Japanese Unexamined Patent Application Publication No. 2009-016543 (published on Jan. 22, 2009).
In Japanese Unexamined Patent Application Publication No. 2005-150041, a light emitting device 101 is proposed, which includes a laser diode 102, a phosphor 103, a first reflection mirror 104, a second reflection mirror 106, and a light-transmitting member 107, and in which fluorescence that is generated by the phosphor 103 is reflected by the second reflection mirror 106, and is emitted to the outside (refer to FIG. 10).
In addition, in Japanese Unexamined Patent Application Publication No. 2004-111909, a light emitting device 201 is proposed, which includes an LED 202, a first reflector 203, a second reflector 204, and a phosphor layer 205, and in which excitation light is collected in a slit 204a by the first reflector 203, and excitation light that is transmitted through the slit 204a is radiated to the phosphor layer 205 (refer to FIG. 11).
In addition, in Japanese Unexamined Patent Application Publication No. 2012-099222, a light emitting device 301 is proposed, which includes a solid state light source 302, a phosphor layer 303, and a diffusion unit 304, and in which the diffusion unit 304 that diffuses excitation light is disposed in the periphery of the phosphor layer 303 (refer to FIG. 12).
In addition, in Japanese Unexamined Patent Application Publication No. 2009-016543, a light emitting device 401 is proposed, which includes a semiconductor light emitting element 402, a wavelength converting member 403, and a cap 404, and in which the wavelength converting member 403 is disposed in a light extraction window of the cap 404 (refer to FIG. 13).
However, the related art as described above has problems in that excitation light or the like is generated but some excitation light is not radiated to a light emitting section, and thereby utilization efficiency of the excitation light is decreased.
That is, in Japanese Unexamined Patent Application Publication No. 2005-150041, the excitation light that is reflected by a surface of the phosphor 103 or the first reflection mirror 104, among the excitation light that is emitted toward the phosphor 103, is reflected by the second reflection mirror 106 and is emitted to the outside in a state of coherent light. Accordingly, excitation light that is used for excitation of the phosphor 103 is reduced.
In addition, in Japanese Unexamined Patent Application Publication No. 2004-111909, not all the excitation light that is transmitted through the slit 204a is radiated to the phosphor layer 205, and part of the excitation light is emitted to the outside of the light emitting device 201. Similarly, in Japanese Unexamined Patent Application Publication No. 2012-099222, the excitation light that is not radiated to the phosphor layer 303 is diffused by the diffusion unit 304 and is emitted to the outside of the light emitting device 301. Accordingly, the excitation light that is used for excitation of the phosphor layers 205 and 303 is reduced.
Furthermore, in Japanese Unexamined Patent Application Publication No. 2009-016543, the excitation light that is not radiated to the wavelength converting member 403 is trapped inside the cap 404, but any unit that may guide the excitation light to the wavelength converting member 403 is not described. Accordingly, it is not possible to efficiently use the excitation light that is not radiated to the wavelength converting member 403 for excitation of the wavelength converting member 403.